US20110156918A1 - System for monitoring oil level and detecting leaks in power transformers, reactors, current and potential transformers, high voltage bushings and the like - Google Patents

System for monitoring oil level and detecting leaks in power transformers, reactors, current and potential transformers, high voltage bushings and the like Download PDF

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US20110156918A1
US20110156918A1 US12/649,741 US64974109A US2011156918A1 US 20110156918 A1 US20110156918 A1 US 20110156918A1 US 64974109 A US64974109 A US 64974109A US 2011156918 A1 US2011156918 A1 US 2011156918A1
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level
oil
oil level
monitor
level monitor
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US8400320B2 (en
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Eduardo Pedrosa Santos
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Priority to EP10840233.0A priority patent/EP2519957B1/en
Priority to ES10840233.0T priority patent/ES2643467T3/en
Priority to BR112012016353A priority patent/BR112012016353B1/en
Priority to PCT/BR2010/000422 priority patent/WO2011079357A1/en
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    • GPHYSICS
    • G01MEASURING; TESTING
    • G01FMEASURING VOLUME, VOLUME FLOW, MASS FLOW OR LIQUID LEVEL; METERING BY VOLUME
    • G01F23/00Indicating or measuring liquid level or level of fluent solid material, e.g. indicating in terms of volume or indicating by means of an alarm
    • G01F23/14Indicating or measuring liquid level or level of fluent solid material, e.g. indicating in terms of volume or indicating by means of an alarm by measurement of pressure
    • G01F23/18Indicating, recording or alarm devices actuated electrically
    • GPHYSICS
    • G01MEASURING; TESTING
    • G01FMEASURING VOLUME, VOLUME FLOW, MASS FLOW OR LIQUID LEVEL; METERING BY VOLUME
    • G01F23/00Indicating or measuring liquid level or level of fluent solid material, e.g. indicating in terms of volume or indicating by means of an alarm
    • G01F23/14Indicating or measuring liquid level or level of fluent solid material, e.g. indicating in terms of volume or indicating by means of an alarm by measurement of pressure
    • G01F23/18Indicating, recording or alarm devices actuated electrically
    • G01F23/185Indicating, recording or alarm devices actuated electrically for discrete levels
    • GPHYSICS
    • G01MEASURING; TESTING
    • G01FMEASURING VOLUME, VOLUME FLOW, MASS FLOW OR LIQUID LEVEL; METERING BY VOLUME
    • G01F23/00Indicating or measuring liquid level or level of fluent solid material, e.g. indicating in terms of volume or indicating by means of an alarm
    • G01F23/80Arrangements for signal processing
    • G01F23/802Particular electronic circuits for digital processing equipment
    • G01F23/804Particular electronic circuits for digital processing equipment containing circuits handling parameters other than liquid level

Definitions

  • Power transformers and reactors are pieces of equipment widely used in medium, high and extra-high voltage electric power generation, transmission and distribution systems. These devices frequently use for insulation and heat removal some type of oil, which can be mineral (petroleum byproduct), vegetal (from soy bean, sunflower or other) or silicon, for example.
  • oil which can be mineral (petroleum byproduct), vegetal (from soy bean, sunflower or other) or silicon, for example.
  • Transformers and reactors have copper coils that are wrapped in paper.
  • the transformer or reactor is equipped with an oil expansion tank, also called a conservation tank, installed above the equipment's main tank and connected to it by piping.
  • the function of the conservation tank is to provide room for the oil level to vary in its interior, rising with increases in temperature and falling with decreases.
  • the volume of the conservation tank is calculated in such a manner that the main tank, where the active part is located, will always be completely full of oil, even at the lowest temperatures, and the oil will never overflow, even at the highest expected temperatures.
  • measuring the oil level permits detecting higher than expected levels due to filling equipment with excess oil; for example, warning of overflow risks and contamination of the environment.
  • the expansion tank is also equipped with a rubber membrane or bag that impedes the oil's direct contact with the air; however, without impeding any variation in oil level, since the membrane or bag is flexible, rising and falling in accordance with the oil level.
  • the upper part of the rubber membrane or bag is in contact with the external environment through air piping and an air dehumidifying mechanism. This avoids pressure or vacuum in the equipment tank due to expansion or contraction of oil.
  • the oil level measuring system is comprised of an oil level indicator that operates using a float located in the lower part of the rubber membrane or bag, so that the float rises and falls accompanying the movement of the membrane or bag, which in turn accompanies the increase or reduction in oil level.
  • the float is coupled to an oil level indicator by a rod that moves a mechanism, which in turn activates the pointer, indicating current oil level at a graduated scale.
  • FIG. 1 Schottrachlorosarcoma —Schematic view of the newly invented monitoring system applied in a transformer
  • FIG. 2 Schott al.
  • FIG. 3 Schott al. 3 —Schematic view of the newly invented monitoring system applied in a transformer with only one or two temperature sensors in the main tank;
  • FIG. 4 Electrical diagram showing oil level measurement and indication without availability of auxiliary power supply.
  • the system is comprised of an electronic pressure sensor ( 21 ) installed in an access opening ( 20 ), which normally already exists in the lower part of the expansion tank ( 4 ) for draining.
  • the sensor ( 21 ) measures oil pressure ( 6 ) at access opening ( 20 ) in relation to atmospheric pressure. Since the air ( 10 ) in the expansion tank ( 4 ) is also at atmospheric pressure, by means of the piping ( 8 ), the pressure measured by the sensor ( 21 ) equals the oil column pressure ( 6 ) in the expansion tank ( 4 ). Therefore, the measurement from the pressure sensor ( 21 ) is proportional to the oil level ( 6 ), which permits measuring the level without using floats or any mechanical parts.
  • the signals ( 23 ) from pressure ( 21 ) and temperature ( 22 ) sensor measurements are then taken to a level monitor ( 24 A) located in the transformer control panel ( 19 ) or a level monitor ( 24 B) located in the expansion tank ( 4 ), adjacent to the pressure and temperature sensors ( 21 , 22 ), so that it can form a mechanical unit with them.
  • the gas relay ( 32 ) also called a Buchholz relay, is installed in the piping ( 5 ) that connects the transformer tank ( 1 ) and the expansion tank ( 4 ).
  • the gas relay ( 32 ) permits oil ( 6 ) to pass through it, aimed at collecting eventual gas bubbles in the oil. Since the gas relay ( 32 ) is in direct contact with the oil ( 6 ) and is installed near the expansion tank ( 4 ), the oil level monitor ( 24 C) can be integrated to the gas relay ( 32 ), with the pressure sensor ( 21 ) installed in the gas relay ( 32 ) and in contact with the oil, just like the temperature sensor ( 22 ).
  • the level monitor ( 24 A, 24 B) corrects the measured pressure value considering the change in oil ( 6 ) density with its temperature, thus obtaining the correct height of the oil column ( 6 ) and consequently, the exact level of oil ( 6 ), which is indicated on the display ( 25 ) of the level monitor ( 24 A, 24 B).
  • the display ( 25 ) can show the oil level information in numerical as well as bar graph format to permit easy visualization from a distance.
  • the level monitor permits the user to program upper and lower limits for the oil level. If the level falls below the lower limit, the level monitor generates a low oil level alarm. Likewise, if the level goes above the upper limit, the level monitor generates a high oil level alarm.
  • the alarms generated may activate one or more electrical alarm contacts ( 26 ) depending on the contact ( 26 ) selection programmed previously by the user for each of the alarms individually, which may be used by the user to activate a visual or sonorous alarm in the installation's control room (not represented).
  • the expansion and contraction of insulating oil occurs as a result of changes in temperature, so that, if there are no leaks, the oil level ( 6 ) in the expansion tank ( 4 ) will be determined by the oil temperature along the height of the transformer tank ( 1 ). Since oil temperature ( 6 ) changes at each different point along tank ( 1 ) height, the level monitoring system described has several temperature sensors ( 27 A, 27 B, 27 C), in various numbers, distributed along tank ( 1 ) height, which are connected to oil level monitor inputs ( 24 A, 24 B).
  • the level monitor ( 24 A, 24 B) uses these temperature measurements to calculate temperature distribution along the entire transformer tank ( 1 ), even in locations where no temperature sensors have been installed, through interpolation and/or extrapolation, using mathematical functions that can be selected from among linear, polynomial and exponential types, among others. With the distribution of temperatures along the tank ( 1 ), the level monitor ( 24 A, 24 B) calculates oil expansion or contraction ( 6 ) along the tank ( 1 ), thus obtaining the expected oil level in the expansion tank ( 4 ).
  • the level monitor ( 24 A, 24 B) permits the installation of only 2 oil temperature sensors at different heights of the tank ( 1 ), then calculates the temperatures at the intermediate heights between sensors by interpolation and calculates the temperatures above the highest sensor ( 27 A) and below the lowest sensor ( 27 C) by extrapolation.
  • the mathematical functions of interpolation and extrapolation used by the level monitor may be selected from among the linear, polynomial and exponential types, among others.
  • the level monitor ( 24 A) can calculate the temperature at the bottom of the tank ( 1 ) by measuring the temperature of the available sensor ( 27 A), of the current that circulates through the transformer, measured by a current transformer ( 31 ), and characteristics the transformer cooling system radiators ( 28 ), thus obtaining a “virtual temperature sensor” ( 27 V) for the bottom of the tank ( 1 ).
  • the already described mathematics interpolation processes can be used to interpolate and extrapolate temperatures along tank height ( 1 ).
  • the oil level monitor ( 24 A, 24 B) then calculates the difference between the real oil level, obtained from pressure ( 21 ) and temperature ( 22 ) sensors, and expected oil level, calculated from temperature sensors ( 27 A, 27 B, 27 C) in the tank ( 1 ), with the difference called Level Error.
  • the level monitor permits the user to program upper and lower limits for the Level Error. If the Level Error falls below the lower limit, the level monitor generates a low oil level alarm. Likewise, if the Error Level goes above the upper limit, the level monitor generates a high oil level alarm.
  • the alarms generated may activate one or more electrical alarm contact ( 26 ) depending on the contact ( 26 ) selection programmed previously by the user for each of the alarms individually.
  • the level monitor calculates the Level Error's average in a moving window with a time frame that can be adjusted by the user. The result is called Average Level Error.
  • the level monitor permits the user to program upper and lower limits for the Average Level Error. If the Average Level Error falls below the lower limit, the level monitor generates a low oil level alarm Likewise, if the Average Error Level goes above the upper limit, the level monitor generates a high oil level alarm.
  • the alarms generated may activate one or more electrical alarm contact ( 26 ) depending on the contact ( 26 ) selection programmed previously by the user for each of the alarms individually.
  • the level monitor ( 24 A, 24 B) continuously calculates the oil level in the expansion tank ( 4 ) if the oil is at a uniform temperature, equal to a reference temperature scheduled by the user, such as 25° C., and where this result is called the Standardized Level.
  • the level monitor permits the user to program upper and lower limits for the Standardized Level. If the Standardized Level falls below the lower limit, the level monitor generates a low oil level alarm. Likewise, if the Standardized Level goes above the upper limit, the level monitor generates a high oil level alarm.
  • the alarms generated may activate one or more electrical alarm contact ( 26 ) depending on the contact ( 26 ) selection programmed previously by the user for each of the alarms individually.
  • the level monitor calculates the Standardized Level's average in a moving window with a time frame that can be adjusted by the user. The result is called the Average Standardized Level.
  • the level monitor permits the user to program upper and lower limits for the Average Standardized Level. If the Average Standardized Level falls below the lower limit, the level monitor generates a low oil level alarm. Likewise, if the Average Standardized Level goes above the upper limit, the level monitor generates a high oil level alarm.
  • the alarms generated may activate one or more electrical alarm contact ( 26 ) depending on the contact ( 26 ) selection programmed previously by the user for each of the alarms individually.
  • the level monitor calculates the tendencies of evolution by unit of time for the Level Error, Average Level Error, Standardized Level and Average Standardized Level parameters. From the calculated tendencies of evolution, and supposing that the same remain constant, the level monitor ( 24 A, 25 B) calculates the number of days left for each of these parameters to reach their own lower limit. The level monitor permits the user to program a lower limit, in days, for the number of calculated days remaining.
  • the level monitor ( 24 A, 24 B) If any of these is less than or equal to the programmed limit, the level monitor ( 24 A, 24 B) generates an alarm by tendency or reduction in the oil level, which activates one or more electrical contacts ( 26 ) according to the selection of contacts ( 26 ) previously programmed by the user for each of the alarms individually.
  • the level monitor ( 24 A, 24 B) has analog outputs ( 26 A).
  • These analog outputs ( 26 A) can adopt a current output standard, such as 0 to 1 mA; 0 to 5 mA; 4 to 20 mA or others, or a standard voltage standard, such as 0 to 1V; 0 to 5V; 0 to 10V or others.
  • the starting and ending values for analog output scales ( 26 A) can be programmed by the user, according to the variable being indicated by the output; for example, if the output is 4 to 20 mA and it is indicating oil level, the beginning of the scale can correspond to a level of 0%, generating a 4 mA signal at the output, and the end of the scale can correspond to a level of 100%, generating a signal of 20 mA at the output.
  • the level monitor ( 24 A) is equipped with an energy accumulator device ( 33 ) that may be a battery, a supercapacitor or other, with sufficient charge to operate the pressure ( 21 ) and temperature ( 22 ) sensors, as well as the reading circuits for these sensors ( 34 ), the microcontroller ( 35 ) and display ( 25 ).
  • an energy accumulator device ( 33 ) may be a battery, a supercapacitor or other, with sufficient charge to operate the pressure ( 21 ) and temperature ( 22 ) sensors, as well as the reading circuits for these sensors ( 34 ), the microcontroller ( 35 ) and display ( 25 ).
  • the level monitor ( 24 A) normally remains turned off and out of operation.
  • the user can request the measurement by activating the button ( 36 ) on the level monitor ( 24 A).
  • a timing circuit is triggered ( 37 ) that sends power to the sensors ( 21 , 22 ), the reading circuit ( 34 ), the microcontroller ( 35 ) and the display ( 25 ) for just enough time for the user to make the reading, automatically turning off these same elements after just a few seconds.
  • the accumulator ( 33 ) is dimensioned so that it has sufficient energy for a large number of readings, and for enough time so that auxiliary power can be brought by cables to the level monitor ( 24 A).
  • the level monitor is installed out of user reach, along ground level, as shown in FIGS. 1 and 2 , in which the level monitor ( 24 B, 24 C) is near the expansion tank ( 4 ) or integrated to the gas relay ( 32 ).
  • the activation button ( 36 A) can be installed separately from the level monitor ( 24 A), so that it can be reached by the user at the ground level.
  • the level monitor ( 24 A) can be equipped with a device for remote activation, without contact, consisting of a photo-detector ( 38 ) installed and pointing in the direction of the ground, so that when excited by a beam of light sent by the user, by means of a flashlight, for example, it sends an electric signal to the timing circuit ( 37 ), which then begins to operate in an identical manner as when activated by the button ( 36 ).
  • a light filter ( 39 ) is installed in front of the photo-detector ( 38 ), in a manner that permits the photo-detector ( 38 ) to be excited only by light of a predetermined wavelength, such as infrared, for example, and blocking out all other wavelengths.

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  • Physics & Mathematics (AREA)
  • Fluid Mechanics (AREA)
  • General Physics & Mathematics (AREA)
  • Engineering & Computer Science (AREA)
  • Signal Processing (AREA)
  • Housings And Mounting Of Transformers (AREA)

Abstract

System for monitoring oil level and detecting leaks in power transformers, reactors, current and potential transformers, high voltage bushings and the like, notably for a system that through the use of sensors and other electronic components measures and monitors transformers and similar equipment in real time, filled with insulating oil, with greater precision and without need for floats or mobile mechanical parts, while presenting countless facilities in the sense of making level monitoring more reliable and safer, highlighting the level error calculations, oil leak detection alarm, excess oil detection alarm during the equipment filling process and calculation of tendencies of evolution for levels among other facilities.

Description

    FIELD OF THE INVENTION
  • This petition for a patent is for an original “SYSTEM FOR MONITORING OIL LEVEL AND DETECTING LEAKS IN POWER TRANSFORMERS, REACTORS, CURRENT AND POTENTIAL TRANSFORMERS, HIGH VOLTAGE BUSHINGS AND THE LIKE”; namely a system that uses sensors and other electronic components to measure and monitor, in real time, transformers and similar equipment filled with insulating oil with greater precision and without any need for floats or other movable, mechanical parts, while also presenting countless facilities in terms of making level monitoring more reliable and safer, highlighting level error calculations, an alarm when detecting oil leaks, or detecting excess oil during the equipment filling process and the calculation of tendencies of evolution for levels, among other facilities.
  • BACKGROUND OF THE INVENTION
  • Power transformers and reactors are pieces of equipment widely used in medium, high and extra-high voltage electric power generation, transmission and distribution systems. These devices frequently use for insulation and heat removal some type of oil, which can be mineral (petroleum byproduct), vegetal (from soy bean, sunflower or other) or silicon, for example.
  • Transformers and reactors have copper coils that are wrapped in paper. The entire active part—comprised of a core and coils—is then immersed in insulating oil to impregnate the paper and thus ensure the electric isolation of the assembly, and to cool the coils with the oil circulating in heat radiators.
  • Thus, for safe operation of the equipment, it is essential for the active part to be permanently immersed in insulating oil. However, temperature variations during equipment operation due to variations in ambient temperature and heating caused by the electric current, make the oil dilate and contract, thus making its volume vary and increasing and reducing oil level.
  • In order to guarantee the active part is permanently immersed in insulating oil during all operating conditions, the transformer or reactor is equipped with an oil expansion tank, also called a conservation tank, installed above the equipment's main tank and connected to it by piping. The function of the conservation tank is to provide room for the oil level to vary in its interior, rising with increases in temperature and falling with decreases. The volume of the conservation tank is calculated in such a manner that the main tank, where the active part is located, will always be completely full of oil, even at the lowest temperatures, and the oil will never overflow, even at the highest expected temperatures.
  • Therefore, given the importance of oil level for safe operation of the equipment, it is necessary to continuously measure it in order to readily detect any level lower than minimum tolerances, thus preventing a short circuit due to lack of oil in the active part, and to warn of environmental contamination with oil due to eventual leaking. Likewise, measuring the oil level permits detecting higher than expected levels due to filling equipment with excess oil; for example, warning of overflow risks and contamination of the environment.
  • In modern transformers and reactors, the expansion tank is also equipped with a rubber membrane or bag that impedes the oil's direct contact with the air; however, without impeding any variation in oil level, since the membrane or bag is flexible, rising and falling in accordance with the oil level. The upper part of the rubber membrane or bag is in contact with the external environment through air piping and an air dehumidifying mechanism. This avoids pressure or vacuum in the equipment tank due to expansion or contraction of oil.
  • In the current state of the art, the oil level measuring system is comprised of an oil level indicator that operates using a float located in the lower part of the rubber membrane or bag, so that the float rises and falls accompanying the movement of the membrane or bag, which in turn accompanies the increase or reduction in oil level. The float is coupled to an oil level indicator by a rod that moves a mechanism, which in turn activates the pointer, indicating current oil level at a graduated scale.
  • This arrangement can be observed for example in U.S. Pat. Nos. 7,191,648 and 6,708,562.
  • When the oil level reaches critical conditions, such as low, very low, high or very high levels, movement of the mechanism closes one or more electrical contacts, which are used to activate a visual or sonorous alarm in the installation control room.
  • The state of the art for the oil level indication system presents some disadvantages observed in practice, which are:
      • Because it is a mechanically activated system, it is subject to mechanical failures such as jamming of the mechanism;
      • In order to prevent mechanical failures, it is necessary to have preventive maintenance for lubrication, for example;
      • With the up and down movement of the oil level, the rubber of the membrane or bag may present undulations or folds in which the float may get caught, leading to the imprecise indication of oil level;
      • In extreme cases, the above described fact may cause the float and/or its rod to perforate the membrane or bag, putting the oil in contact with oxygen and humidity in the air and causing the accelerated aging of the isolation paper on the coils by oxidation and hydrolysis;
      • Leak detection cannot be conducted immediately since the loss of oil to the environment may be masked by an increase in level due to temperature increases, so the alarm contacts for low levels will only be activated after a considerable volume of oil has been disposed of in nature;
      • Likewise, detection of a transformer that has been overfilled with oil cannot be done immediately since the existence of excess oil can be masked by the reduction in oil level due to low temperatures when the transformer is shut off. Thus, the contacts will only be activated some time after the transformer has been energized, when the temperature rises, causing the forced shut down of the equipment for removal of oil or the leaking of excess oil into the environment.
    SUMMARY OF THE INVENTION
  • Aware of the state of art, its inconveniences and limitations, the inventor, active in the segment of matters in hand, studies and research, created the “SYSTEM FOR MONITORING OIL LEVEL AND DETECTING LEAKS IN POWER TRANSFORMERS, REACTORS, CURRENT AND POTENTIAL TRANSFORMERS, HIGH VOLTAGE BUSHINGS AND THE LIKE” in question, which makes the real time measuring and monitoring of oil levels in transformers and similar equipment filled with isolation oil more reliable and without the use of floats and mechanical parts, solving the current deficiencies amply referred to and illustrated in the state of the art.
  • The oil monitoring system in question has the following advantages in relation to the state of the art:
      • Since it does not have moving mechanical parts, problems associated with mechanical failure and maintenance needs are eliminated;
      • Since it does not have a float or other parts in contact with the rubber membrane or bag, the risk of the level measuring system to damage or perforate those items is eliminated;
      • Greater precision in measuring the oil level since it does not use a mechanical system;
      • Able to integrate with other already existing protection or monitoring equipment in the transformer or reactor, such as the gas accumulation relay (buchholz relay) and temperature monitor, reducing costs and facilitating installation and maintenance;
      • Improved monitoring of eventual oil leaks, permitting their detection even before the oil level reaches the minimum limit. It thus provides less risk of failure for the transformer or reactor and a reduction in environmental impact in case of a leak;
      • Permits detecting excess filling of the transformer or reactor with oil, even if the oil level does not reach the maximum limit due to low temperature.
    BRIEF DESCRIPTION OF THE FIGURES
  • The invention will now be explained in detail through the drawings listed below:
  • FIG. 1—Schematic view of the newly invented monitoring system applied in a transformer;
  • FIG. 2—Schematic view of the newly invented monitoring system applied in a transformer with a gas accumulation relay attached;
  • FIG. 3—Schematic view of the newly invented monitoring system applied in a transformer with only one or two temperature sensors in the main tank;
  • FIG. 4—Electric diagram showing oil level measurement and indication without availability of auxiliary power supply.
  • DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
  • The “SYSTEM FOR MONITORING OIL LEVEL AND DETECTING LEAKS IN POWER TRANSFORMERS, REACTORS, CURRENT AND POTENTIAL TRANSFORMERS, HIGH VOLTAGE BUSHINGS AND THE LIKE”, for measuring and monitoring insulating oil levels of transformers and similar equipment, using an oil level monitor (24A, 24B) to which a pressure sensor (21), to measure internal oil column pressure (6), and a temperature sensor (22), arranged to measure oil temperature (6) in the expansion tank (4), are connected, so that the level monitor (24A, 24B) calculates oil column height, which corresponds to the oil level, from the oil pressure and takes into account the change in oil density with temperature, precisely indicating the oil level (6) on the display (25).
  • The system, as shown in FIG. 1, is comprised of an electronic pressure sensor (21) installed in an access opening (20), which normally already exists in the lower part of the expansion tank (4) for draining. The sensor (21) measures oil pressure (6) at access opening (20) in relation to atmospheric pressure. Since the air (10) in the expansion tank (4) is also at atmospheric pressure, by means of the piping (8), the pressure measured by the sensor (21) equals the oil column pressure (6) in the expansion tank (4). Therefore, the measurement from the pressure sensor (21) is proportional to the oil level (6), which permits measuring the level without using floats or any mechanical parts.
  • The signals (23) from pressure (21) and temperature (22) sensor measurements are then taken to a level monitor (24A) located in the transformer control panel (19) or a level monitor (24B) located in the expansion tank (4), adjacent to the pressure and temperature sensors (21, 22), so that it can form a mechanical unit with them.
  • As shown in FIG. 2, the gas relay (32), also called a Buchholz relay, is installed in the piping (5) that connects the transformer tank (1) and the expansion tank (4). The gas relay (32) permits oil (6) to pass through it, aimed at collecting eventual gas bubbles in the oil. Since the gas relay (32) is in direct contact with the oil (6) and is installed near the expansion tank (4), the oil level monitor (24C) can be integrated to the gas relay (32), with the pressure sensor (21) installed in the gas relay (32) and in contact with the oil, just like the temperature sensor (22).
  • With the information from the pressure (21) and oil temperature (22) sensors in the tank (4), the level monitor (24A, 24B) corrects the measured pressure value considering the change in oil (6) density with its temperature, thus obtaining the correct height of the oil column (6) and consequently, the exact level of oil (6), which is indicated on the display (25) of the level monitor (24A, 24B). The display (25) can show the oil level information in numerical as well as bar graph format to permit easy visualization from a distance.
  • The level monitor permits the user to program upper and lower limits for the oil level. If the level falls below the lower limit, the level monitor generates a low oil level alarm. Likewise, if the level goes above the upper limit, the level monitor generates a high oil level alarm. The alarms generated may activate one or more electrical alarm contacts (26) depending on the contact (26) selection programmed previously by the user for each of the alarms individually, which may be used by the user to activate a visual or sonorous alarm in the installation's control room (not represented).
  • As explained, the expansion and contraction of insulating oil occurs as a result of changes in temperature, so that, if there are no leaks, the oil level (6) in the expansion tank (4) will be determined by the oil temperature along the height of the transformer tank (1). Since oil temperature (6) changes at each different point along tank (1) height, the level monitoring system described has several temperature sensors (27A, 27B, 27C), in various numbers, distributed along tank (1) height, which are connected to oil level monitor inputs (24A, 24B). Using these temperature measurements, the level monitor (24A, 24B) calculates temperature distribution along the entire transformer tank (1), even in locations where no temperature sensors have been installed, through interpolation and/or extrapolation, using mathematical functions that can be selected from among linear, polynomial and exponential types, among others. With the distribution of temperatures along the tank (1), the level monitor (24A, 24B) calculates oil expansion or contraction (6) along the tank (1), thus obtaining the expected oil level in the expansion tank (4).
  • Since the installation of a large number of oil temperature sensors (27A, 27B, 27C) along the transformer tank (1) may not be feasible in practice, the level monitor (24A, 24B) permits the installation of only 2 oil temperature sensors at different heights of the tank (1), then calculates the temperatures at the intermediate heights between sensors by interpolation and calculates the temperatures above the highest sensor (27A) and below the lowest sensor (27C) by extrapolation. The mathematical functions of interpolation and extrapolation used by the level monitor may be selected from among the linear, polynomial and exponential types, among others.
  • In applications where only one temperature sensor (27A) is available at the top of transformer tank oil (1), as shown in FIG. 3, the level monitor (24A) can calculate the temperature at the bottom of the tank (1) by measuring the temperature of the available sensor (27A), of the current that circulates through the transformer, measured by a current transformer (31), and characteristics the transformer cooling system radiators (28), thus obtaining a “virtual temperature sensor” (27V) for the bottom of the tank (1). With the information from the real temperature sensor (27A) and the “virtual sensor” (27V), the already described mathematics interpolation processes can be used to interpolate and extrapolate temperatures along tank height (1). This possibility is especially interesting when considering that oil temperature measurement (27A) at the top of the tank (1) and from the current transformer (31) are already available in temperature monitors (29) that normally equip power transformers, which permits the integration of oil level monitor (24A) and transformer temperature monitor (29) functions in the same monitoring system.
  • The oil level monitor (24A, 24B) then calculates the difference between the real oil level, obtained from pressure (21) and temperature (22) sensors, and expected oil level, calculated from temperature sensors (27A, 27B, 27C) in the tank (1), with the difference called Level Error. The level monitor permits the user to program upper and lower limits for the Level Error. If the Level Error falls below the lower limit, the level monitor generates a low oil level alarm. Likewise, if the Error Level goes above the upper limit, the level monitor generates a high oil level alarm. The alarms generated may activate one or more electrical alarm contact (26) depending on the contact (26) selection programmed previously by the user for each of the alarms individually.
  • Given that the Level Error is subject to oscillations over time, caused by imprecision inherent to sensors (21, 22, 27A, 27B, 27C), the level monitor calculates the Level Error's average in a moving window with a time frame that can be adjusted by the user. The result is called Average Level Error. The level monitor permits the user to program upper and lower limits for the Average Level Error. If the Average Level Error falls below the lower limit, the level monitor generates a low oil level alarm Likewise, if the Average Error Level goes above the upper limit, the level monitor generates a high oil level alarm. The alarms generated may activate one or more electrical alarm contact (26) depending on the contact (26) selection programmed previously by the user for each of the alarms individually.
  • Alternatively, with the temperature distribution along the tank (1) height, obtained from the interpolation and extrapolation processes described above, the level monitor (24A, 24B) continuously calculates the oil level in the expansion tank (4) if the oil is at a uniform temperature, equal to a reference temperature scheduled by the user, such as 25° C., and where this result is called the Standardized Level. The level monitor permits the user to program upper and lower limits for the Standardized Level. If the Standardized Level falls below the lower limit, the level monitor generates a low oil level alarm. Likewise, if the Standardized Level goes above the upper limit, the level monitor generates a high oil level alarm. The alarms generated may activate one or more electrical alarm contact (26) depending on the contact (26) selection programmed previously by the user for each of the alarms individually.
  • Given that the Standardized Level is subject to oscillations over time, caused by imprecision inherent to sensors (21, 22, 27A, 27B, 27C), the level monitor calculates the Standardized Level's average in a moving window with a time frame that can be adjusted by the user. The result is called the Average Standardized Level. The level monitor permits the user to program upper and lower limits for the Average Standardized Level. If the Average Standardized Level falls below the lower limit, the level monitor generates a low oil level alarm. Likewise, if the Average Standardized Level goes above the upper limit, the level monitor generates a high oil level alarm. The alarms generated may activate one or more electrical alarm contact (26) depending on the contact (26) selection programmed previously by the user for each of the alarms individually.
  • Since one of the main purposes of a level monitoring system is to detect oil loss from leaks into the environment, and considering that leaks with little oil flow may persist over a long time before any of the aforementioned alarm limits are reached, the level monitor (24A, 24B) calculates the tendencies of evolution by unit of time for the Level Error, Average Level Error, Standardized Level and Average Standardized Level parameters. From the calculated tendencies of evolution, and supposing that the same remain constant, the level monitor (24A, 25B) calculates the number of days left for each of these parameters to reach their own lower limit. The level monitor permits the user to program a lower limit, in days, for the number of calculated days remaining. If any of these is less than or equal to the programmed limit, the level monitor (24A, 24B) generates an alarm by tendency or reduction in the oil level, which activates one or more electrical contacts (26) according to the selection of contacts (26) previously programmed by the user for each of the alarms individually.
  • In order to permit the remote indication of Oil Level, Error Level, Average Error Level, Standardized Level and Average Standardized Level information, as well as tendencies of evolution in these same parameters in the installation's control room or SCADA type supervisory systems, the level monitor (24A, 24B) has analog outputs (26A). These analog outputs (26A) can adopt a current output standard, such as 0 to 1 mA; 0 to 5 mA; 4 to 20 mA or others, or a standard voltage standard, such as 0 to 1V; 0 to 5V; 0 to 10V or others. The starting and ending values for analog output scales (26A) can be programmed by the user, according to the variable being indicated by the output; for example, if the output is 4 to 20 mA and it is indicating oil level, the beginning of the scale can correspond to a level of 0%, generating a 4 mA signal at the output, and the end of the scale can correspond to a level of 100%, generating a signal of 20 mA at the output.
  • In certain situations, it may be necessary for oil level measurement and indication to be available without any auxiliary power voltage (40) available for the level monitor (24A, 24B). This is the case, for example, during the transformer filling process with oil, when the electrical connections that would take power to the level monitor (24A, 24B) are not yet available. In order to permit operation in this situation, as shown in FIG. 4, the level monitor (24A) is equipped with an energy accumulator device (33) that may be a battery, a supercapacitor or other, with sufficient charge to operate the pressure (21) and temperature (22) sensors, as well as the reading circuits for these sensors (34), the microcontroller (35) and display (25). In order to maximize the duration of the energy accumulated in the accumulator device (33), the level monitor (24A) normally remains turned off and out of operation.
  • Whenever it is necessary to measure the level, the user can request the measurement by activating the button (36) on the level monitor (24A). By activating the button (36) a timing circuit is triggered (37) that sends power to the sensors (21, 22), the reading circuit (34), the microcontroller (35) and the display (25) for just enough time for the user to make the reading, automatically turning off these same elements after just a few seconds. The accumulator (33) is dimensioned so that it has sufficient energy for a large number of readings, and for enough time so that auxiliary power can be brought by cables to the level monitor (24A).
  • However, there are applications where the level monitor is installed out of user reach, along ground level, as shown in FIGS. 1 and 2, in which the level monitor (24B, 24C) is near the expansion tank (4) or integrated to the gas relay (32). As shown in FIG. 4, for these applications, the activation button (36A) can be installed separately from the level monitor (24A), so that it can be reached by the user at the ground level.
  • Alternatively, the level monitor (24A) can be equipped with a device for remote activation, without contact, consisting of a photo-detector (38) installed and pointing in the direction of the ground, so that when excited by a beam of light sent by the user, by means of a flashlight, for example, it sends an electric signal to the timing circuit (37), which then begins to operate in an identical manner as when activated by the button (36). In order to avoid improper activation, a light filter (39) is installed in front of the photo-detector (38), in a manner that permits the photo-detector (38) to be excited only by light of a predetermined wavelength, such as infrared, for example, and blocking out all other wavelengths.
  • Other remote activation systems, without contact, can be employed in replacement of the photo-detector (38), such as audible or inaudible sounds, radiofrequency waves, laser beams, visible or invisible light or others, which will operate in a similar manner, allowing the user to send a request from a distance.

Claims (24)

1. A system for monitoring oil level and detecting leaks in power transformers, reactors, current and potential transformers, high voltage bushings and the like, the system comprising an oil level monitor to which a pressure sensor is installed at an access opening in a lower part of an expansion tank to measure internal oil column pressure, and a temperature sensor, arranged in a manner to measure oil temperature in the tank; the level monitor calculating oil column height, which corresponds to oil level, from the oil column pressure taking into account a change in oil density with temperature, the oil level monitor further obtaining a precise oil level and indicating it on a display; the level monitor generating a low level alarm when a programmed lower limit is reached or a high level alarm when a programmed upper level has been reached.
2. The system according to claim 1 wherein the level monitor presents oil level information on a display in numerical as well as bar graph format to permit easy visualization from a distance.
3. The system according to claim 1 further comprising installation of a pressure sensor and a temperature sensor in a gas accumulation relay, in contact with the oil, permitting integration of the oil level monitor and gas relay functions in the same system.
4. The system according to claim 1 wherein the level monitor is in the transformer's control panel.
5. The system of claim 1, wherein the level monitor is in the expansion tank, adjacent to the pressure and temperature sensors, forming a mechanical unit with them.
6. The system of claim 1, wherein the level monitor is integrated to the gas relay.
7. The system according to claim 1, wherein the oil level monitor has inputs to connect several temperature sensors distributed along a height of a transformer tank and is adapted to use temperature measurements from the temperature sensors to calculate a distribution of temperatures along the entire transformer tank, the level monitor being adapted to calculate the expansion or contraction of the oil along the tank using the distribution of temperatures along the tank, thus obtaining the expected oil level in the expansion tank.
8. The system according to claim 7, wherein using an expected oil level, the oil level monitor can calculate a Level Error by a difference between the real oil level and the expected oil level, generating a low oil level alarm if the Level Error is less than a lowest programmed limit, or a high oil level alarm if the Level Error is greater than a programmed upper limit.
9. The system according to claim 7, wherein the oil level monitor can calculate an Average Level Error by a moving window average of the Level Error in a window of time that can be adjusted by a user, generating a low oil level alarm if the Average Level Error is less than the lowest programmed limit, or a high oil level alarm if the Average Level Error is greater than the programmed upper limit.
10. The system according to claim 7, wherein the oil level monitor permits the installation of an upper and a lower oil temperature sensors at different heights of the tank, and further wherein the oil level monitor calculates temperatures at intermediate heights between the sensors using interpolation and calculates temperatures above the upper sensor and below the lower sensor by extrapolation.
11. The system according to claim 7, wherein the oil level monitor permits the installation of one temperature sensor at a top of the transformer tank and calculates the temperature at a bottom of the transformer tank by measuring the temperature of the one sensor, measuring a current that flows through the transformer, measured using a current transformer, and using the characteristics of the radiators in the transformer's cooling system, thus obtaining a virtual temperature sensor at a lower part of the tank; with the information from the one and virtual temperature sensors being used to interpolate and extrapolate the temperatures along the height of the tank.
12. The system according to claim 11, wherein oil level monitor is integrated with the temperature monitor in order to use the information from the one oil temperature sensor and the current transformer, permitting the integration of oil level monitor and transformer temperature monitor functions in the same monitoring system.
13. The system according to claim 7, wherein the oil level monitor uses a temperature distribution along the height of the tank to continuously calculate a Standardized Level, which corresponds to the oil level that would exist in the expansion tank if the oil was at a uniform temperature and equal to a reference temperature programmed by the user, generating a low oil level alarm if the Standardized Level is less than a lowest programmed limit, or a high oil level alarm if the Standardized Level is higher than a programmed upper limit.
14. The system according to claim 13, wherein the oil level monitor calculates an Average Standardized Level by a moving window average of the Standardized Level in a window of time that can be adjusted by the user, generating a low oil level alarm if the Average Standardized Level is less than the lowest programmed limit, or a high oil level alarm if the Average Standardized Level is higher than the programmed upper limit.
15. The system according to claim 8, wherein the oil level monitor calculates tendencies for evolution by unit of time for the Level Error parameter, and uses these tendencies of evolution calculate the number of days remaining for this parameter to reach its lower limit; the level monitor permits programming a lower limit, in days, for the number of days remaining calculated by the tendencies of evolution, generating an alarm for a tendency for reduction in oil level if any of the days remaining is less than or equal to the minimum limit.
16. The system according to claim 1, wherein the oil level monitor permits selecting electric contacts to be activated when there is an incident involving low oil level, high oil level or tendency for reduction in oil level alarms, and wherein programming is done individually for each of the alarms listed.
17. The system according to claim 1, wherein the oil level monitor permits selecting which parameters from among Oil Level, Level Error, Average Level Error, Standardized Level and Average Standardized Level options, as well as tendencies for evolution of these same parameters, will be indicated for each of a plurality of analog outputs; the oil level monitor allowing programming of beginning and end of scale values for the analog outputs, according to the parameter being indicated by the analog output.
18. The system according to claim 1, wherein the oil level monitor, is equipped with an energy accumulator device, with sufficient charge to permit the operation of pressure and temperature sensors, as well as reading circuits for these sensors, for a microcontroller and for a display, enabling oil level measurement and indication to be available when the level monitor is without auxiliary power voltage.
19. The system according to claim 18, wherein the level monitor normally remain is turned off and out of operation in order to maximize a duration of accumulated energy in the accumulator device, wherein a user can request a measurement of the oil level by activating a button in the level monitor; wherein when this button is activated it triggers a timing circuit, that sends power to the sensors, a reading circuit, the microcontroller the display just long enough for the reading to be made by the user, and turns off these same elements automatically after a few seconds; the accumulator device being dimensioned so that its energy will be sufficient for a large number of level monitor readings.
20. The system according to claim 19, wherein the activation button is installed separately from the level monitor, in a location that can be reached by the user at ground level.
21. The system according to claim 19, wherein the level monitor has a photo-detector that points towards the ground, so that when excited by a beam of light sent by the user, it sends an electric signal to a timing circuit, which then begins to operate in an identical manner as when the button is activated, permitting remote activation, without contact.
22. The system according to claim 21, wherein a light filter is installed in front of the photo-detector, that permits the photo-detector to be hit only by light of a predetermined wavelength and blocking the passage of other wavelengths, thus avoiding improper activations of the timing circuit.
23. The system according to claim 18, wherein a remote, no contact, activation system sends an electric signal to a timing circuit that sends power to the pressure sensors, temperature sensors, a reading circuit, the microcontroller and the display long enough for a reading to be made by a user and turns off these same elements automatically after a few seconds.
24. The system of claim 23, wherein the remote no contact activation system is chosen from the group consisting of: audible or inaudible sound waves, radio frequency waves, laser beams, and visible or invisible light.
US12/649,741 2009-12-30 2009-12-30 System for monitoring oil level and detecting leaks in power transformers, reactors, current and potential transformers, high voltage bushings and the like Active 2031-06-12 US8400320B2 (en)

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US12/649,741 US8400320B2 (en) 2009-12-30 2009-12-30 System for monitoring oil level and detecting leaks in power transformers, reactors, current and potential transformers, high voltage bushings and the like
EP10840233.0A EP2519957B1 (en) 2009-12-30 2010-12-20 System for monitoring oil level and detecting leaks in power transformers, reactors, current and potential transformers, high voltage bushings and similar.
ES10840233.0T ES2643467T3 (en) 2009-12-30 2010-12-20 System to monitor the oil level and detect leaks in power transformers, reactors, current and potential transformers, high voltage insulators and the like
BR112012016353A BR112012016353B1 (en) 2009-12-30 2010-12-20 system for oil level monitoring and leak detection in power transformers, reactors, current and potential transformers, high voltage bushings and the like
PCT/BR2010/000422 WO2011079357A1 (en) 2009-12-30 2010-12-20 System for monitoring oil level and detecting leaks in power transformers, reactors, current and potential transformers, high voltage bushings and similar.

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Cited By (59)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN102636317A (en) * 2012-05-02 2012-08-15 四川省南充晶塔变压器有限公司 Leakage testing device of gas-liquid two-phase transformer oil tank
US20120326880A1 (en) * 2011-06-23 2012-12-27 Hamilton Sundstrand Corporation Low Oil Indication
KR101232267B1 (en) 2012-12-18 2013-02-15 제동일 Densitometer
US20140013734A1 (en) * 2012-03-15 2014-01-16 Aes Engineering Limited Mechanical seal support system
CN103996492A (en) * 2014-05-08 2014-08-20 昆山佑翔电子科技有限公司 Pre-alarm transformer based on transformer oil monitoring
CN104198130A (en) * 2014-09-19 2014-12-10 国家电网公司 SF6 gas leakage detection method base on fractional laser-induced breakdown spectroscopy
CN104614013A (en) * 2014-12-26 2015-05-13 合肥通用机械研究院 Automatic identification method of major hazard source of storage tank
AU2012294518B2 (en) * 2011-08-09 2015-08-13 Economy Polymers & Chemicals System effective to monitor an amount of chemicals in portable container
CN105047373A (en) * 2015-08-25 2015-11-11 重庆民生变压器有限责任公司 Straight-tube high-elevation cyclic heat dissipation transformer
CN105070473A (en) * 2015-08-26 2015-11-18 国网山东省电力公司淄博供电公司 Electrified oiling device for distribution transformer
US20170089340A1 (en) * 2015-04-29 2017-03-30 Emerson Climate Technologies, Inc. Compressor Having Oil-Level Sensing System
CN106840429A (en) * 2017-03-27 2017-06-13 上海置信电气非晶有限公司 A kind of device of link-type duplex measurement temperature and liquid level
DE102015225303A1 (en) * 2015-12-15 2017-06-22 Vega Grieshaber Kg Runtime sensor with long-term energy storage
CN107622804A (en) * 2017-10-17 2018-01-23 中国核动力研究设计院 A kind of method to set up of fuel element rupture detection alarming value
US20180080889A1 (en) * 2016-08-26 2018-03-22 Hiwin Technologies Corp. Lubrication detection method for linear motion system
EP3299783A1 (en) * 2016-09-23 2018-03-28 ABB Schweiz AG Thermal monitoring of a power device
CN107894265A (en) * 2017-12-05 2018-04-10 国网福建省电力有限公司泉州供电公司 A kind of transformer device for monitoring oil level
CN108288531A (en) * 2018-01-09 2018-07-17 国网山东省电力公司滨州供电公司 A kind of transformer oil level auxiliary conditioning unit
CN108390356A (en) * 2018-03-21 2018-08-10 广东电网有限责任公司电力科学研究院 A kind of grave gas guard method based on fault time feature
WO2019000804A1 (en) * 2017-06-30 2019-01-03 广东合一新材料研究院有限公司 Electromagnetic coil cooling system
US10192677B2 (en) 2014-08-12 2019-01-29 Abb Inc. Method and apparatus for leakage monitoring for oil-immersed electrical transformers
CN109489770A (en) * 2018-11-29 2019-03-19 国网上海市电力公司 Intelligent transformer oil level detection system based on pressure capsule system
CN109579940A (en) * 2018-12-20 2019-04-05 李佳迪 Power transformer oil conservater oil level detection method and device
DE102018102951A1 (en) * 2018-02-09 2019-08-14 Rheinisch-Westfälische Technische Hochschule (Rwth) Aachen Method and system for in-process calculation of a three-dimensional temperature distribution
CN110361144A (en) * 2019-07-31 2019-10-22 洛阳博泰机车装备有限公司 Harmonious locomotive main transformer test technology equipment and method
CN110459431A (en) * 2019-09-04 2019-11-15 上海乐研电气有限公司 A kind of shock type teletransmission gas density relay
EP3671997A1 (en) * 2018-12-20 2020-06-24 ABB Schweiz AG System for monitoring a switchgear
CN111351548A (en) * 2020-04-28 2020-06-30 南京智鹤电子科技有限公司 Oil level monitoring device
CN111429676A (en) * 2020-03-10 2020-07-17 国网浙江省电力有限公司金华供电公司 Oil leakage monitoring system and accident oil pool structure of transformer substation
EP3702746A1 (en) * 2019-03-01 2020-09-02 ABB Power Grids Switzerland AG High voltage system comprising a temperature distribution determining device
CN111856167A (en) * 2019-04-19 2020-10-30 宁波奥克斯高科技有限公司 Detection method of box-type transformer and transformer
CN111929516A (en) * 2020-06-30 2020-11-13 国网黑龙江省电力有限公司电力科学研究院 Reactor low-temperature resistance detection system and detection method based on optical fiber sensor
EP3745098A1 (en) 2019-05-29 2020-12-02 ABB Power Grids Switzerland AG Method for measuring a quantity of liquid in a liquid-insulated electrical component, liquid-insulated electrical component and railroad vehicle having the same
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WO2023077862A1 (en) * 2021-11-06 2023-05-11 国网山西省电力公司电力科学研究院 Transformer oil conservator defect monitoring device and detection method based on edge computing
CN117219410A (en) * 2023-08-27 2023-12-12 南通兴安源金属制品有限公司 Transformer tank with oil mass induction structure
CN117629313A (en) * 2024-01-26 2024-03-01 南京中鑫智电科技有限公司 On-line monitoring method and system for oil expansion of converter transformer valve side sleeve

Families Citing this family (11)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
ES2546906T3 (en) 2011-07-11 2015-09-29 Abb Technology Ag Optical sensor structure for the detection of water or oil leaks inside a conservator that has a chamber or membrane
CN103196496A (en) * 2013-04-03 2013-07-10 国家电网公司 Automatic monitoring and protecting device for oil temperature and oil level of power transformer
US20140305201A1 (en) * 2013-04-12 2014-10-16 Joe David Watson Electronic liquid level sensing device and gauge for liquid-immersed power transformers, reactors and similar equipment
US9377341B1 (en) * 2013-04-12 2016-06-28 Joe David Watson Electronic liquid level sensing device and gauge for liquid-immersed power transformers, reactors and similar equipment
CN103414156A (en) * 2013-07-09 2013-11-27 内蒙古鄂尔多斯联合化工有限公司 Oil immersed transformer light gas protection fault diagnosis method
CN103605294B (en) * 2013-09-07 2015-12-02 国家电网公司 With the transformer Buchholz relay of wireless remote means of deflation
DE102015204431A1 (en) * 2015-03-12 2016-09-15 Alstom Technology Ltd. Method and device for monitoring an oil filling of a power transformer
GB201705039D0 (en) 2017-03-29 2017-05-10 Weston Aerospace Ltd A Liquid level monitoring system
WO2020019056A1 (en) 2018-07-27 2020-01-30 Reseau Synapse Inc. Instantaneous water/oil separation system
US11328862B1 (en) 2019-07-17 2022-05-10 Ubicquia, Inc. Distribution transformer monitor
CN111751056B (en) * 2020-07-08 2022-05-10 江苏华辰变压器股份有限公司 Detection process for leakage test of transformer oil tank

Citations (14)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US1920037A (en) * 1930-09-01 1933-07-25 Tauber Konrad Differential safety device for transformers and the like
US2704841A (en) * 1951-01-08 1955-03-22 Mcgraw Electric Co Combined current responsive and temperature responsive alarm device for transformers
US3449633A (en) * 1967-03-07 1969-06-10 Westinghouse Electric Corp Electrical transformer
US4201089A (en) * 1976-10-08 1980-05-06 Elin-Union Aktiengesellschaft Temperature measuring device for transformers and reactors
US4654806A (en) * 1984-03-30 1987-03-31 Westinghouse Electric Corp. Method and apparatus for monitoring transformers
US4868547A (en) * 1988-09-06 1989-09-19 Georgia Power Company Transformer alarm annunciator
JPH05283240A (en) * 1992-04-01 1993-10-29 Toshiba Corp Oil-filled transformer
US5842149A (en) * 1996-10-22 1998-11-24 Baker Hughes Incorporated Closed loop drilling system
US6909349B1 (en) * 1999-11-17 2005-06-21 Trexco, Llc Apparatus and method for cooling power transformers
US7049922B2 (en) * 2001-12-05 2006-05-23 Insoil Canada Ltd. Method and apparatus for decreasing gassing and decay of insulating oil in transformers
US20090216464A1 (en) * 2008-02-21 2009-08-27 Korea Institute Of Science & Technology Integrated in-line oil monitoring apparatus
US20090231075A1 (en) * 2008-03-12 2009-09-17 Alstom Transport Sa Oil cooling system, particularly for transformers feeding traction electric motors, transformer with said system and method for determining the cooling fluid flow in a cooling system
US20100313849A1 (en) * 2009-06-11 2010-12-16 Michael Anthony Stoner Fault Detection and Mitigation in Hybrid Drive System
US7928741B2 (en) * 2006-02-17 2011-04-19 Voelker Senors, Inc. Oil monitoring system

Family Cites Families (11)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US5333498A (en) * 1992-06-19 1994-08-02 W. L. Walker Co., Inc. Apparatus and method for measuring physical characteristics of a liquid
FR2739486B1 (en) * 1995-09-28 1997-11-14 Magnier Philippe METHOD AND DEVICE FOR PROTECTION AGAINST EXPLOSION AND FIRE OF ELECTRICAL TRANSFORMERS
FR2747245B1 (en) * 1996-04-04 1998-05-15 Gec Alsthom T & D Sa SYSTEM FOR PROTECTING AN INSULATED THREE-PHASE DISTRIBUTION TRANSFORMER IN A LIQUID DIELECTRIC
DE50200302D1 (en) 2001-11-22 2004-04-22 Messko Albert Hauser Gmbh & Co level indicator
DE10224186B4 (en) * 2002-05-31 2007-04-12 Areva T&D Sa Through a liquid to insulated and / or cooled on-load tap-changer for connecting and disconnecting windings of a transformer
UA61173C2 (en) * 2003-05-15 2003-11-17 Oleksandr Mykolaiov Rassalskyi Device for controlling parameters of a power transformer
ES2298894T3 (en) 2004-10-14 2008-05-16 Maschinenfabrik Reinhausen Gmbh FLUID FILLING LEVEL INDICATOR.
BRPI0502206A (en) * 2005-06-01 2007-01-23 Junko Hiraoka electronic gas relay
JP4936923B2 (en) * 2007-02-20 2012-05-23 株式会社東芝 Stationary guidance device and stationary guidance device monitoring device
DE102007028704B4 (en) * 2007-06-21 2011-06-16 Areva Energietechnik Gmbh Method for monitoring the oil filling of an electrical transformer
CN101577173A (en) * 2008-05-06 2009-11-11 上海置信电气非晶有限公司 Oil immersion type distribution transformer with winding temperature measurement function

Patent Citations (14)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US1920037A (en) * 1930-09-01 1933-07-25 Tauber Konrad Differential safety device for transformers and the like
US2704841A (en) * 1951-01-08 1955-03-22 Mcgraw Electric Co Combined current responsive and temperature responsive alarm device for transformers
US3449633A (en) * 1967-03-07 1969-06-10 Westinghouse Electric Corp Electrical transformer
US4201089A (en) * 1976-10-08 1980-05-06 Elin-Union Aktiengesellschaft Temperature measuring device for transformers and reactors
US4654806A (en) * 1984-03-30 1987-03-31 Westinghouse Electric Corp. Method and apparatus for monitoring transformers
US4868547A (en) * 1988-09-06 1989-09-19 Georgia Power Company Transformer alarm annunciator
JPH05283240A (en) * 1992-04-01 1993-10-29 Toshiba Corp Oil-filled transformer
US5842149A (en) * 1996-10-22 1998-11-24 Baker Hughes Incorporated Closed loop drilling system
US6909349B1 (en) * 1999-11-17 2005-06-21 Trexco, Llc Apparatus and method for cooling power transformers
US7049922B2 (en) * 2001-12-05 2006-05-23 Insoil Canada Ltd. Method and apparatus for decreasing gassing and decay of insulating oil in transformers
US7928741B2 (en) * 2006-02-17 2011-04-19 Voelker Senors, Inc. Oil monitoring system
US20090216464A1 (en) * 2008-02-21 2009-08-27 Korea Institute Of Science & Technology Integrated in-line oil monitoring apparatus
US20090231075A1 (en) * 2008-03-12 2009-09-17 Alstom Transport Sa Oil cooling system, particularly for transformers feeding traction electric motors, transformer with said system and method for determining the cooling fluid flow in a cooling system
US20100313849A1 (en) * 2009-06-11 2010-12-16 Michael Anthony Stoner Fault Detection and Mitigation in Hybrid Drive System

Cited By (70)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US20120326880A1 (en) * 2011-06-23 2012-12-27 Hamilton Sundstrand Corporation Low Oil Indication
US8446284B2 (en) * 2011-06-23 2013-05-21 Pratt & Whitney Low oil indication
AU2012294518B2 (en) * 2011-08-09 2015-08-13 Economy Polymers & Chemicals System effective to monitor an amount of chemicals in portable container
US20140013734A1 (en) * 2012-03-15 2014-01-16 Aes Engineering Limited Mechanical seal support system
CN102636317A (en) * 2012-05-02 2012-08-15 四川省南充晶塔变压器有限公司 Leakage testing device of gas-liquid two-phase transformer oil tank
KR101232267B1 (en) 2012-12-18 2013-02-15 제동일 Densitometer
CN103996492A (en) * 2014-05-08 2014-08-20 昆山佑翔电子科技有限公司 Pre-alarm transformer based on transformer oil monitoring
US10192677B2 (en) 2014-08-12 2019-01-29 Abb Inc. Method and apparatus for leakage monitoring for oil-immersed electrical transformers
CN104198130A (en) * 2014-09-19 2014-12-10 国家电网公司 SF6 gas leakage detection method base on fractional laser-induced breakdown spectroscopy
CN104614013A (en) * 2014-12-26 2015-05-13 合肥通用机械研究院 Automatic identification method of major hazard source of storage tank
US10125768B2 (en) 2015-04-29 2018-11-13 Emerson Climate Technologies, Inc. Compressor having oil-level sensing system
US20170089340A1 (en) * 2015-04-29 2017-03-30 Emerson Climate Technologies, Inc. Compressor Having Oil-Level Sensing System
US10180139B2 (en) * 2015-04-29 2019-01-15 Emerson Climate Technologies, Inc. Compressor having oil-level sensing system
CN105047373A (en) * 2015-08-25 2015-11-11 重庆民生变压器有限责任公司 Straight-tube high-elevation cyclic heat dissipation transformer
CN105070473A (en) * 2015-08-26 2015-11-18 国网山东省电力公司淄博供电公司 Electrified oiling device for distribution transformer
DE102015225303A1 (en) * 2015-12-15 2017-06-22 Vega Grieshaber Kg Runtime sensor with long-term energy storage
US10502610B2 (en) 2015-12-15 2019-12-10 Vega Grieshaber Kg Propagation time sensor comprising a long-term energy store
US20180080889A1 (en) * 2016-08-26 2018-03-22 Hiwin Technologies Corp. Lubrication detection method for linear motion system
US10379099B2 (en) * 2016-08-26 2019-08-13 Hiwin Technologies Corp. Lubrication detection method for linear motion system
EP3299783A1 (en) * 2016-09-23 2018-03-28 ABB Schweiz AG Thermal monitoring of a power device
CN106840429A (en) * 2017-03-27 2017-06-13 上海置信电气非晶有限公司 A kind of device of link-type duplex measurement temperature and liquid level
WO2019000804A1 (en) * 2017-06-30 2019-01-03 广东合一新材料研究院有限公司 Electromagnetic coil cooling system
CN107622804A (en) * 2017-10-17 2018-01-23 中国核动力研究设计院 A kind of method to set up of fuel element rupture detection alarming value
CN107894265A (en) * 2017-12-05 2018-04-10 国网福建省电力有限公司泉州供电公司 A kind of transformer device for monitoring oil level
CN108288531A (en) * 2018-01-09 2018-07-17 国网山东省电力公司滨州供电公司 A kind of transformer oil level auxiliary conditioning unit
DE102018102951A1 (en) * 2018-02-09 2019-08-14 Rheinisch-Westfälische Technische Hochschule (Rwth) Aachen Method and system for in-process calculation of a three-dimensional temperature distribution
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CN109489770A (en) * 2018-11-29 2019-03-19 国网上海市电力公司 Intelligent transformer oil level detection system based on pressure capsule system
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EP3671997A1 (en) * 2018-12-20 2020-06-24 ABB Schweiz AG System for monitoring a switchgear
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